Broadband down-conversion of near-infrared emission in Bi3+-Yb3+ co-doped Y3Al5O12 phosphors

An efficient near-infrared (NIR) down-conversion (DC) process has been demonstrated in Bi3+-Yb3+ co-doped Y3Al5O12 phosphors. The excitation spectra, emission spectra and decay curves were measured to prove the occurrence of energy transfer (ET) from Bi3+ → Yb3+. Upon the excitation of UV photons, NIR emission has been obtained at 1028 nm through the energy transfer from 3P1 energy level of Bi3+ to 2F5/2 energy level of Yb3+. Quantum efficiency related to Yb3+ concentration is calculated and the maximum efficiency reaches 138%. Our results suggested that these phosphors might have a potential application for the down-conversion process to improve the efficiency of Si-based solar cells.